The present invention relates to a ventilation device such as a duct quarter vent for preventing the pressure in a vehicle passenger compartment from increasing when the doors are shut.
A prior art ventilation device 100 shown in FIGS. 8 to 10(b) is attached to an opening formed in an inconspicuous part of a rear section of a vehicle. The ventilation device 100 has a duct main body 21 attached to the opening of the vehicle. The duct main body 21 has openings 22. Insertion slots 23 are formed in an upper edge of the duct main body 21. The insertion slots 23 are spaced at a predetermined interval. A valve body 24 is formed of an elastic material such as a rubber sheet. Substantially triangular engaging pieces 25 are provided at an end of the valve body 24. The engaging pieces 25 are spaced at a predetermined interval. When each engaging piece 25 is inserted in the corresponding insertion slot 23, side sections of the engaging piece 25 project by a great amount from the sides of the insertion slot 23. As a result, the valve body 24 is hung from the duct main body 21 such that the valve body 24 selectively opens and closes the openings 22.
When the valve body 24 is attached to the duct main body 21, each engaging piece 25 is entirely flexed as shown in FIG. 10(a). Particularly, the side sections of each engaging piece 25 are flexed at a relatively small curvature. The insertion causes the engaging pieces 25 to receive a great resistance, which makes the attaching of the valve body 24 burdensome.
To eliminate such a drawback, the width W of each insertion slot 23 shown in FIG. 10(a) may be increased to reduce the resistance. However, the widened width W cause the engaging piece 25 to easily come off the slot 23.
To reduce the resistance applied to each engaging piece 25 by the corresponding insertion slot 23, Japanese Laid-Open Patent Publication No. 7-179118 discloses a ventilation device 101 shown in FIG. 11. In this configuration, the upper end 23a of each insertion slot 23 is chamfered. Each engaging piece 25 of the valve body 24 is easily engaged with the corresponding insertion slot 23 through the upper end 23a. In accordance with the difference between the pressure in the passenger compartment and the outside pressure, each valve body 24 is moved in a range of opening width X of the corresponding insertion slots 23.
However, the engaging force of the engaging pieces 25 and the insertion slots 23 is weak in the ventilation device 101 shown in FIG. 11, and the engaging pieces 25 easily come off the slots 23 as in the case where the width W of the slots 23 is increased. Particularly, when the valve body 24 is moved away from the openings 22, the valve body 24 lies along the plane containing the upper ends 23a. Since the thickness t of the valve body 24 is less than the opening width X of the insertion slots 23, the engaging pieces 25 are likely to come off the insertion slots 23.